<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>

  <body>
    <body>
      <div id="app">
        <h2 class="title" :class="[active, line]">{{message}}</h2>
        <h2 class="title" :class="getClasses()">{{message}}</h2>
      </div>

      <script src="../js/vue.js"></script>
      <script>
        const app = new Vue({
          el: '#app',
          data: {
            message: '你好',
            active: 'a',
            line: 'b'
          },
          methods: {
            getClasses: function () {
              return [this.active, this.line]
            }
          }
        })
      </script>
    </body>
  </body>
</html>
